19th Iranian Chemistry Congress , 2017-02-21

Title : ( Catalyst-free dehalogenation of 5-bromopyrimidine derivatives using DMF/trialkylamine as the hydrogen source )

Authors: Mahsa Mousavi , Mehdi Bakavoli , Ali Shiri , Hossein Eshghi ,

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Introduction: A wide range of synthetically valuable transformations in organic chemistry involve reduction process through which functionalization can be easily performed over the course of the reaction. While several reduction methodologies utilizing transition metals as catalysts, non-catalytic methods are of more interest as they offer safe and inexpensive synthetic protocols. Reports on dehalogenation of halo-uracils involve photochemical reductions through irradiation in aqueous alcoholic solvents [1-4], thermolysis in acetamide [5], sonication in the presence of Indium metal[6], and reduction under physiological conditions [7-8]. Experimental:A mixture of 5-bromo-2,4-diamino-6-substituted pyrimidine and trialkylamin in DMF was heated with stirring over the range of 80 – 120 °C. After the completion of the reaction, the solvent was evaporated under reduced pressure and the product was purified by column chromatography.Result and discussion: The reaction of halogenated pyrimidines with the mixture of DMF/R3N gives rise to the dehalogenated product. The reaction can be completed within hours and the obtained product can be easily purified by column chromatography. The optimum temperature for this reaction is set on 80 to 120°C. Other trialkylamine also was tested to efficiently work in this reaction as well. To propose a mechanism we referred to the frequently reported publications wherein amines are well-known as efficient electron-donors in Electron Transfer catalytic reactions [9,10]. Owing to the molecular orbital theory calculations which considers pyrimidine as a moderate electron acceptor [11], it is estimated that temperature could have initiated the Electron Transfer process (Thermal Electron Transfer); leading to a single electron transfer from Et3N-DMF complex to the 5-bromopyrimidine. At least 10 several derivatives of 5-halogenopyrimidines and uracil were successfully reduced under the same reaction conditions. In all cases emerging a singlet signal between 5-6 ppm in 1H NMR and a signal at 91 ppm in 13C NMR besides other spectral characterizations, strongly confirms the replacement of bromide with a hydrogen atom in the product.Conclusion:We have developed a novel metal catalyst-free procedure for reduction of 5-bromo pyrimidinesusing Et3N/DMF as a potential reducing system. To the best of our knowledge this is the first report of dehalogenation reaction using DMF, in the absence of metals. The system can tolerate amine and sulfide functionalities. Our results may provide a new route to the reduction of more other organic compounds.References: [1] B. Matasovic, M. Bonifacic. Radiation Phys. Chem., 2011, 80, 750–754. [2] B. J. Swanson, J. C. Kutzer, T. H. Koch. J. Am. Chem. Soc, 1981, 103, 1274-1276. [3] T. M. Dietz, T. H. Koch. Photochem. Photobio., 1989, 49, 121-129. [4] L. Venkatarangan, D.H Yang, G. A. Epling, A. K. Basu. Tetrahedron Lett., 1999, 40, 1441-1444. [5] M. Sako, M. Suzuki, M. Tanabe, Y. Maki. J. Chem. Soc., Perkin Trans. 1, 1981, 3114- 3117. [6] K. Tanaka, T. Kamei, A. Okamoto. Tetrahedron Lett., (2007), 48, 3167–3169. [7] S. Mondal, D. Manna, G. Mugesh. Angew.Chem. Int. Ed, 2015, 54, 9298 –9302. [8] H. W. Barrett, R. A. West. J. Am. Chem. Soc, 1956, 78, 1612–1615. [9] S. Nad, H. Pal, J. Chem. Phys, 2002.116, 1658-1670. [10] J. Hu, J. Wang, T. Nguyen, N. Zheng, Beilstein J. Org. Chem, 2013, 9,1977–2001. [11] B. Pullman, A. Pullman, Biochemistry, 1958, 44, 1197-1202.

Keywords

, Catalyst-free dehalogenation, 5-bromopyrimidine, hydrogen
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@inproceedings{paperid:1061918,
author = {Mousavi, Mahsa and Bakavoli, Mehdi and Shiri, Ali and Eshghi, Hossein},
title = {Catalyst-free dehalogenation of 5-bromopyrimidine derivatives using DMF/trialkylamine as the hydrogen source},
booktitle = {19th Iranian Chemistry Congress},
year = {2017},
location = {شیراز, IRAN},
keywords = {Catalyst-free dehalogenation; 5-bromopyrimidine; hydrogen source},
}

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%0 Conference Proceedings
%T Catalyst-free dehalogenation of 5-bromopyrimidine derivatives using DMF/trialkylamine as the hydrogen source
%A Mousavi, Mahsa
%A Bakavoli, Mehdi
%A Shiri, Ali
%A Eshghi, Hossein
%J 19th Iranian Chemistry Congress
%D 2017

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